1. Field of the Invention
The present invention relates to a process-oriented modulized plant for TFT-LCD fabrication and that is capable of modulizing fabs corresponding to the characteristics of the manufacturing processes. The modulized plant is provided to avoid cross contaminations between the processes.
2. Description of Related Art
As the TFT-LCD technology progresses, particulates are no longer the main factor that causes defects of microelectronic devices and circuits. The cross contaminations existing between different processes have gradually become another important factor that causes the defects. For example, the thin film process is subject to the contamination of organic or acid gases, which affect the yield, yet the photolithography process produces these organic gases. Moreover, the photolithography process is influenced by temperature, humidity, and microvibrations that may lower the yield, but the thin film process is exactly a high heat-releasing process. Therefore, if the thin film process and the photolithography process are arranged in the same space, the temperature interferences and the cross contaminations will arise.
Several processes in a TFT-LCD factory are exemplified below. The thin film process is a high heat-releasing process with low cleanliness requirement (FED Std 209E Class 10,000). Its purity, level of airborne molecular contamination, is subject to contaminations of organic or acidic gases. The photolithography process is influenced by microvibrations, temperature and humidity. The requirement of temperature/humidity, 23±1 (or 2)° C./55%±1 (or 2)% should be met by the photolithography process. Its cleanliness requirement (FED Std 209E Class 100 or Class 10) is higherthan that of the thin film process, but the photolithography process is a source of organic gases. The etching process is hardly affected by temperature and humidity. Its cleanliness requirement (FED Std 209E Class 10,000 or 100,000) is lower than that of the photolithography process. However, the etching process is a source of acidic and alkaline gases. The stripping process is also hardly affected by temperature and humidity, and its cleanliness (FED Std 209E Class 10,000 or 100,000) is lower than that of the photolithography process. The stripping process is a source of stripper, which contains organic gases.
To summarize the above statements, if different processes are placed together without appropriate separation or arrangement, the cross contaminations between different processes will inevitably arise and the yield will deteriorate greatly.
A conventional common optoelectronic factory is basically divided into four process areas: array, color filter, cell, and module. All processes of each process area are located in the same building. The more advance the generation of the TFT-LCD technology is, the larger the substrate is. Thus, following problems resulted from the large substrate will arise:                1. More serious cross contaminations between the different processes for larger substrates occurr, while the different processes are located in the same process area. Even separations are carefully established in the site, contaminants in the air will spread via an automated material handling system.        2. Facilities would be damaged quickly by fire accidents or smoke pollutions. All processes of TFT-LCD fabrication are arranged in their respective floors in the same building, and the equipment of these processes may be damaged at the same time by fire accidents or smoke pollutions. Moreover, the insurance fee would increase for this reason.        3. The whole-plant expenses and construction cost increase significantly, because the substrate is large and it is necessary to enlarge the fab area for each process. The quantity of work to establish the factory increases, and the construction schedule is prolonged. In consideration of the investment and market timing, shortening construction schedule will bring about poor quality or industrial safety accidents of the project.        4. Buildings with excessive height waste money. All existent advanced-generation TFT-LCD factories utilize an automated material handling system to link up all of the processes arranged in respective floors of the same building. In order to store large quantity of substrates per unit area, an automatic transport-and-stock system should be built as the tallest equipment through the whole building. If the automatic transport-and-stock system is arranged with the process tools in the same building, the height of building accommodating the automatic transport-and-storage system may be unnecessary and can be lowered in some areas.        5. The initial and operation costs of HVAC (Heating, Ventilation and Air Condition) system must meet the highest cleanliness class required by particular processes, such as the photolithography process, because all of the processes are arranged in the same building. The HVAC system, which is over-designed but not corresponding to the practical cleanliness of various processes, results in wastingmoney.        6. Very high level of microvibration control for the whole building increases construction cost. Usually, processes with high requirements for microvibration control are only limited to specific areas, and the most stringent microvibration criterion is applied to the whole building. Such design concept is only appropriate for the past small-sized substrates. However, for new generation of TFT LCD, the building is larger than before so the past microvibration design concept for building is not suitable and makes unnecessary in crease in construction cost.        7. Risks of extension of construction schedule and increases of safety problems will occur. For new generation of TFT LCD, large-sized substrates need large-sized tools. Some problems come about: one is the large-sized tools are difficult to move in and should be assembled at the site. Therefore, the large-sized tools should move in after the clean room has been built up. Besides, the construction schedule of the large-sized factory is longer than that of the small-sized factory. After the completion of the large-sized tools in the large-sized factory, the market timing may be missed. Another one is the existing building has only a few number of move-in ports in the same floor for transporting large-sized tools. Hence, the move-in schedule will be prolonged and the industrial safety problems may arise.        
Accordingly, the present invention aims to design a plant to solve the above problems in the prior art.